1. Field of the Invention
Embodiments of the present invention relate to heating devices and fuel vapor processing apparatus using the heating devices.
2. Description of the Related Art
JP-A-2009-156030 teaches a known heating device used for a fuel vapor processing apparatus. The heating device disclosed in this document includes a PTC unit and a pair of heat radiation plates disposed at opposite surfaces of the heating unit. The PTC unit includes a sheet-like PTC ceramic material with polyimide films provided as insulation layers on opposite surfaces of the PCT ceramic material. The PTC ceramic material may generate heat by receiving a supply of an electric power. The PTC unit is clamped between the pair of heat radiation plates by crimping the heat radiation plates together in a state that the PTC unit is positioned therebetween.
In the known heating device, the heat radiation plates are brought to contact the polyimide films of the PTC unit as the heat radiation plates are crimped. However, the hat radiation plates are not adhered or bonded to the polyimide films. Therefore, it may be possible that the polyimide films and the heat radiation plates do not closely contact with each other to cause loss of heat conducted from the PTC ceramic material to the heat radiation plates via the polyimide films. This may result in low heat conductivity from the PTC unit to the heat radiation plates. To this end, the polyimide films and the corresponding heat radiation plates may be joined together by using a special adhesive material. However, in such a case, the manufacturing cost may be increased due to the use of the special adhesive material.
Therefore, there has been a need in the art for an improved technique of reducing loss of heat conducted from a heating element to heat radiation plates via insulation layers of the heating element.